A sudden, unexplainable descent from 1500 feet asl immediately preceded the aircraft's impact with the terrain. The aircraft recovered from a steep, nose-down, spiral dive to a near-level attitude just before impact; such a recovery would require the integrity of the aircraft control system and the airframe structure. All of the aerofoil surfaces were at the crash site, and all failures of structural and control components were overload failures. It can, therefore, be concluded that the rapid descent was not the result of an airframe or control system failure. The rapid descent that preceded the crash could have been caused by an intentional act on the part of the pilot. However, it would be unusual for a pilot to change his altitude that abruptly, without clearance, while operating in a control zone and being actively monitored by radar systems and air traffic control personnel. Results of a post-mortem examination confirmed that the pilot had advanced coronary artery disease and that he had other cardiovascular problems that would have increased his risk of sudden incapacitation or cardiac death. These medical indicators, the rapid and unexplained descent, and the lack of any radio coordination with air traffic control make it likely that the pilot suffered physiological distress or incapacitation, which precipitated the rapid descent and the subsequent crash. Procedures and protocols are in place to evaluate and monitor the medical status of pilots. Despite the presence of known cardiovascular risk factors, the pilot was not subject to related restrictions or increased medical monitoring.Analysis A sudden, unexplainable descent from 1500 feet asl immediately preceded the aircraft's impact with the terrain. The aircraft recovered from a steep, nose-down, spiral dive to a near-level attitude just before impact; such a recovery would require the integrity of the aircraft control system and the airframe structure. All of the aerofoil surfaces were at the crash site, and all failures of structural and control components were overload failures. It can, therefore, be concluded that the rapid descent was not the result of an airframe or control system failure. The rapid descent that preceded the crash could have been caused by an intentional act on the part of the pilot. However, it would be unusual for a pilot to change his altitude that abruptly, without clearance, while operating in a control zone and being actively monitored by radar systems and air traffic control personnel. Results of a post-mortem examination confirmed that the pilot had advanced coronary artery disease and that he had other cardiovascular problems that would have increased his risk of sudden incapacitation or cardiac death. These medical indicators, the rapid and unexplained descent, and the lack of any radio coordination with air traffic control make it likely that the pilot suffered physiological distress or incapacitation, which precipitated the rapid descent and the subsequent crash. Procedures and protocols are in place to evaluate and monitor the medical status of pilots. Despite the presence of known cardiovascular risk factors, the pilot was not subject to related restrictions or increased medical monitoring. It is likely the pilot suffered some form of physiological distress or incapacitation that resulted in his losing control of the aircraft.Findings as to Causes and Contributing Factors It is likely the pilot suffered some form of physiological distress or incapacitation that resulted in his losing control of the aircraft. The pilot had advanced coronary artery disease and suffered a number of other cardiovascular problems that would have increased the risk of sudden incapacitation or cardiac death. Despite the presence of known cardiovascular risk factors, no increased medical monitoring or related restrictions were being applied to this pilot.Findings as to Risk The pilot had advanced coronary artery disease and suffered a number of other cardiovascular problems that would have increased the risk of sudden incapacitation or cardiac death. Despite the presence of known cardiovascular risk factors, no increased medical monitoring or related restrictions were being applied to this pilot. On 08 May 2001, the TSB sent Aviation Safety Advisory No.615-A010023-1 to Transport Canada regarding the effectiveness of administrative procedures for the monitoring and follow-up of pilot medical assessments. Transport Canada's response, received 21June2001, indicates that it is taking action to address the issues.Safety Action Taken On 08 May 2001, the TSB sent Aviation Safety Advisory No.615-A010023-1 to Transport Canada regarding the effectiveness of administrative procedures for the monitoring and follow-up of pilot medical assessments. Transport Canada's response, received 21June2001, indicates that it is taking action to address the issues.